An ethmoid mucocele causing diplopia

RATIONALE: Mucocele is a disease lined primarily by epithelium, and occurs mainly when the sinus ostium is obstructed. PATIENT CONCERNS: We report a case of a 37-year-old man who presented with painless proptosis of the right eye and diplopia. DIAGNOSES: The preoperative finding was mucocele of the ethmoid sinus. INTERVENTIONS: We performed endoscopic sinus surgery, which included uncapping of the anterior and superior wall of the mucocele. OUTCOMES: The mucocele was treated safely and effectively without touching the medial orbital wall. LESSONS: Clinicians should note that minimally invasive surgery to remove ethmoid mucoceles is relatively straightforward and can prevent the various complications associated with these lesions.